Golf club head

ABSTRACT

The head of a golf club is improved by reducing the drag and wake turbulence produced in the air when the golf club is swung to strike a golf ball. The club head has a convex sole with an elongated depression defined therein. The inboard end of the depression is located proximate both the heel and the ball-impact face and extends outwardly at a diverging angle from the ball-impact face to an outboard extremity located inboard from the toe of the club head. This depression or channel is thereby closely aligned with the direction of travel of the club head during a normal downswing and follow through of a golf stroke. Also, the top of the club head is covered with a relatively rough coating, such as a textured paint with granules encapsulated therein. The roughness average of the top surface of the club head, as measured by a profilometer, is it least three times as great as that of the ball-impact face and at least three times as great as that of the sole of the club head.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an improved construction for a golf club head. The invention has particular applicability to the types of golf clubs used to drive golf balls long distances, such as a driver.

[0003] 2. Description of the Prior Art

[0004] A wide variety of golf club head configurations have been devised over the years in efforts to aid golfers in enhancing their proficiency in playing the game of golf. While golf club heads have been manufactured in many different shapes, virtually all golf club heads have the same basic parts. Specifically, a golf club head is comprised of a ball impact face, a sole, a top, a heel, a toe, and a back

[0005] Also, golf club heads designed for use on clubs for shots of prescribed distances have certain similarities to each other. For example, the heads of golf club drivers and mashies are relatively massive. These club heads typically have a width of between about five and ten centimeters as measured across the sole from the ball impact face to the back and a length of about seven to eleven centimeters as measured across the sole between the heel and the toe of the club head. A golf club head for a driver typically weighs between about one hundred forty grams and about three hundred forty grams.

[0006] Within these basic measurement ranges there are a wide variety of golf club head configurations. One golf club head configuration which is designed to reduce drag for a wood type golf club is described in U.S. Pat. No. 4,850,593. The golf club head described in this patent has a trough or groove defined in its sole which is aligned to extend generally parallel to the ball-impact face across the entire length of the sole from the heel to the toe of the club head. One defect in this design, however, is that with the normal follow through of a driving stroke the trough is oriented at a very significant angle relative to the path of travel of the club head through the air. As a consequence, airflow past the sole of the club head as the club head moves through the air is more or less perpendicular to the direction of alignment of the trough on the club head sole. This actually increases the turbulence of the air in the wake of the club head passing through the air. As a consequence, an inordinate amount of the power of the stroke is expended in disturbing the air through which the club passes.

[0007] Also, in the design of prior art golf club heads, it is known that the club head surface and outer surface structure is an integral part of the golf club head and overall golf club. The accepted belief in golf club head design is that the outer surface of the head should be as smooth as possible so as to minimize air resistance as the head is swung through the air to drive a golf ball a long distance. The concept has been that a smooth outer surface of a golf club head will facilitate airflow past the head surface. The goal in golf club head design is to produce a golf club head which generates the least possible air resistance in its movement, particularly movement at high velocity. To this end golf club heads have typically been designed with as smooth an outer surface as possible without measurable surface roughness or texture.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide an improved golf club head having both a superior shape or configuration and also a novel and superior surface texture coating. To this end the structure and surface treatment of a golf club head are altered from prior designs to manipulate and reduce surface airflow and turbulence over the surface of the club head both during the downswing phase of the golf stroke at which the club head reaches its maximum velocity, and also during the follow through once the ball has been hit. This reduction in surface airflow turbulence is achieved by the formation of a trough in the club head sole having a unique alignment relative to the ball-impact face and also by coating portions of the club head with a granular or textured coating. Each of these features assists in the breakup of airflow and reduces the drag vacuum so that the club head travels faster and becomes more stable during both the downswing and the follow through. The improved surface texture coating and the creation of a trough in the sole of the club head that is substantially aligned with the direction of club head travel during the entire stroke improves the Reynolds numbers for the club head. Reynolds numbers are used by aeronautical engineers to show a measurement of air drag on an object.

[0009] Contrary to conventional wisdom, it has been discovered, according to the present invention, that a smooth outer surface on the golf club head produces greater air resistance and wake turbulence than a golf club head covered with a textured or granulated surface coating that exhibits a certain degree of roughness. It has been discovered, according to the present invention, that air turbulence is particularly reduced if the top of the golf club head is coated with a granulated coating. Air turbulence is further reduced if this granulated coating is applied to the back of the club head as well.

[0010] The degree or extent of surface roughness of a golf club head is measured with a profilometer using the “Ra” scale, which is calibrated in microns. Roughness readings on the “Ra” scale represent the arithmetical mean of all profile values. This measure of roughness is also known as “roughness average”. In determining roughness average according to the present invention data was collected using a Perthen profilometer.

[0011] In one broad aspect the present invention may be considered to be an improvement in a golf club head having a ball-impact face, a sole, a top, a back, a heel, a toe, and a hozzle. According to the improvement of the invention a depressed channel is defined in the sole and extends from an inboard extremity thereof proximate both the heel and the ball-impact face outwardly at a divergent angle from the ball-impact face to an outboard extremity located inboard from the toe. This channel should be aligned at an angle of between about thirty-five and about sixty-five degrees relative to the ball-impact face. The angle of alignment is preferably about fifty degrees. Also, the channel does not extend all the way to across the sole, but terminates well short of the toe of the club head.

[0012] In another broad aspect the invention may be considered to be an improvement in a golf club head having a ball-impact face, a sole having a convex surface, a top, a back, a heel, a toe, and a hozzle. According to the improvement of the invention, an elongated, concave depression is defined in the convex surface of the sole. The concave depression is aligned to extend from a location at the heel end proximate the ball-impact face away from the heel and at an acute angle of between about thirty-five and sixty-five degrees relative to the ball-impact face and terminates inboard from the toe of the club head. The concave depression or channel is preferably between about two and about three centimeters in width, between about five and about seven centimeters in length, and is between about two and about four millimeters in maximum depth.

[0013] In still another broad aspect, the invention may be considered to be an improvement in a golf club head having a ball-impact face, a sole, a top, a back, a heel, a toe, and a hozzle. According to the improvement of the invention the ball-impact face has an arithmetic mean of profile roughness of between about 0.67 and about 0.81 microns, the sole has an arithmetic mean of profile roughness of between about 0.82 and about 1.1 microns, and the top has an arithmetic mean of profile roughness at least about three times as great as that of the ball-impact face and it least about three times as great as that of the sole. The top preferably has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns. Preferably also the back has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns.

[0014] The invention may be described with greater clarity and particularity by reference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view illustrating a preferred embodiment of a golf club head according to the invention mounted on the shaft of a golf driver.

[0016]FIG. 2 is a front elevational view of the golf club head of FIG. 1 shown in isolation.

[0017]FIG. 3 is a rear elevational view of the golf club head of FIG. 2.

[0018]FIG. 4 is a top plan view of the golf club head of FIG. 2.

[0019]FIG. 5 is a bottom plan view of the golf club head of FIG. 2.

[0020]FIG. 6 is an end view as seen from the toe of the club head of FIG. 2.

[0021]FIG. 7 is an end view as seen from the heel of the club head of FIG. 2.

DESCRIPTION OF THE EMBODIMENT

[0022]FIG. 1 illustrates a PD 901 titanium golf club head 10 mounted upon the lower extremity of a golf club shaft 12 of a golf driver. The golf club head 10 has a substantially planar ball-impact face 14, a convex top surface 16, a convex sole 18 illustrated in FIG. 5, a back 20 located opposite the ball-impact face 14, a heel 22, and a toe 24. The golf club head 10 also has a hozzle 26 located at the top of the heel 22 at the junction between the heel 22 and the top surface 16. As in conventional golf clubs, the hozzle 26 defines a tubular opening therewithin to receive the cylindrical attachment tip of the golf club shaft 12.

[0023] The golf club head 10 is preferably formed of aluminum and titanium and is fabricated as a two-part hollow casting. The general overall size and shape of the golf club head 10 is fairly conventional. The sole is about 7.5 centimeters in width as measured between the ball-impact face 14 and the back 20 at the transition between the sole 18 and the back 20. The top surface 16 is about 11.5 centimeters in length as measured from the base of the hozzle 26 to the transition between the top surface 16 and the toe 24. The club head 10 weighs about two hundred fifty grams when detached from the golf club shaft 12. The sole 18 has a convex surface that extends from the heel 22 in a gradual, smooth transition therewith to the toe 24 and the back 20. The transition of the convex surface of the sole 18 with the back 20 and toe 24 is also quite gradual. Like the sole 18, the top surface 16 also has a slightly convex surface configuration.

[0024] The shape of the club head 10 does differ in several important respects from the shape of conventional golf club heads, however. The sole 18 of the golf club head 10 has a concave trough, depression, or channel 28 formed in its otherwise convex, downwardly facing surface. The depression 28 has an inboard end 30 that extends from a location at the bottom of the heel 22 and proximate the ball-impact face 14, away from the heel 22 and at an acute angle relative to the ball-impact face 14. The longitudinal alignment of the depression 28 may be considered to be determined by the straight line 32 in the plan view projection of FIG. 5 that extends from the inboard end 30 of the trough 28 through the outboard end 34 thereof. The line 32 longitudinally bisects the plan view projection of the channel or depression 28 with one-half of the area of the plan view projection of the depression 28 lying on each side of the line 32 as illustrated in FIG. 5. This plane is perpendicular to the ball-impact face 14.

[0025] While there is a very slight convex curvature to the ball-impact face 14, for purposes of defining the orientation of the alignment of the channel 28, the ball-impact face 14 may be considered to be defined by the plane 36 shown in FIGS. 4, 5, 6, and 7. One-half of the surface area of the ball-impact face 14 lies on each side of the plane 36. However, no portion of that surface area is more than about three millimeters from the plane 36.

[0026] The channel 28 is aligned at an acute angle relative to the ball-impact face 14, as defined by the intersection of the line 32 of alignment of the depression 28 with the ball-impact face plane 36. The range of this angle of intersection can be between about thirty-five degrees and about sixty-five degrees. The preferred alignment of the channel or depression 28 relative to the ball-impact face plane 36 is preferably about fifty degrees.

[0027] The concave depression 28 extends to a depth of between about two and four millimeters at its maximum. The greatest depth of the depression 28 is at the midpoint of the segment of the line 32 line that extends between the extremities of the inboard end 30 and the outboard end 34 within the depression 28. The depression 28 is between about five centimeters and seven centimeters in length and between about two centimeters and about three centimeters in maximum width. The preferred length of the depression 28 is about six centimeters and the preferred maximum width is about two and one-half centimeters.

[0028] It should be noted that the depression 28 does not extend entirely across the sole 18. To the contrary, it terminates well short of the toe 24 of the club head 10, as best shown in FIG. 3. In the embodiment shown, the outboard end 34 of the depression 28 terminates at a distance of about three centimeters from the bottom of the toe 24, as measured along the line 32. The demarcation between the sole 18 and the toe 24 may be considered to be the line of transition between the upper and outboard roughened area 39, indicated by stippling and described hereafter, and the lower and inboard smooth area 41 of the golf club head 10.

[0029] The golf club head 10 differs from conventional golf club heads in other aspects as well. Specifically, both the top surface 16 and the back surface 20, as well as the toe 24 are covered with a granulated, textured paint which creates a certain roughness on these surfaces. This area of roughness is indicated at 39 by stippling in the drawing figures. The ball-impact face 14 is quite smooth and has an arithmetic mean of profile roughness as measured by a profilometer of between about 0.67 microns and about 0.81 microns. The surface of the sole 18 is also quite smooth and has an arithmetic mean of profile roughness of between about 0.82 microns and about 1.1 microns.

[0030] In contrast, the top surface 16 has an arithmetic mean of profile hardness at least about three times as great as that of the ball-impact face 14 and at least about three times as great as that of the sole 18. More specifically, the top has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns. This roughness preferably increases from a maximum near the hozzle 26 to a minimum at the transition with the toe 24. At the location 38 on the top surface 16 near the hozzle 26 the arithmetic mean of profile roughness or roughness average is about 3.87 microns. This roughness decreases to about 3.55 microns at the location 40 near the center of the top surface 16, and decreases further to a roughness average of about 3.33 microns at the transition 42 to the toe 24. The toe 24 also has a roughness average of about 3.33 microns, and is indicated by stippling in the drawing figures.

[0031] The roughness average of the ball-impact face 14 also varies with distance from the hozzle 26. At the top of the ball-impact face 14, indicated at 44, the roughness average is 0.67 microns. The roughness increases slightly to about 0.81 microns at the center 46 of the ball-impact face surface 14, but decreases to about 0.78 microns at its transition 48 to the sole 18.

[0032] The roughness average also varies across the surface of the sole 18. Specifically, in the area 50 between the inboard end 30 of the depression 28 and the ball-impact face 14, the roughness average is about 1.1 microns. Within the depression 28 the roughness average is about 0.82 microns. At the outboard portion 52 of the sole 18 the roughness average is about 0.84 microns.

[0033] When the golf club driver is swung to hit a golf ball, the golf club head 10 moves more smoothly through the air and creates less wake turbulence and vacuum than a conventional golf club head. As a consequence, the club head 10 will move with a greater speed and under more accurate control as contrasted with the movement of the head of a conventional golf club swung in the same stroke. The presence and the configuration and orientation of the channel or depression 28 and also the modification of the surface roughness of several portions of the golf club head 10 thereby improve the power and accuracy of a golfer's driving game.

[0034] Undoubtedly, numerous variations and modifications of the invention will become readily apparent to those familiar with golf club head design. For example, the precise dimensions and orientation of the elongated, shallow depression 28 in the otherwise convex surface of the sole 18 will vary with different sizes and shapes of golf club heads. Also, the exact roughness average across the various surfaces of the golf club head will likewise vary depending upon the size and shape of the club head. Accordingly, the scope of the invention should not be construed as limited to the specific embodiment depicted and described, but rather as defined in the claims appended hereto. 

I claim:
 1. In a golf club head having a ball-impact face, a sole, a top, a back, a heel, a toe, and a hozzle, the improvement wherein a depressed channel is defined in said sole and extends from an inboard extremity thereof proximate both said heel and said ball-impact face outwardly at a diverging angle from said ball-impact face to an outboard extremity located inboard from said toe.
 2. A golf club head according to claim 1 further characterized in that said ball-impact face is substantially flat and said channel is aligned at an angle of between about thirty degrees and about sixty degrees relative to said ball-impact face.
 3. A golf club head according to claim 2 wherein said channel is between about two centimeters and about three centimeters in width and is aligned at an angle of about forty-five degrees relative to said ball-impact face.
 4. A golf club head according to claim 1 wherein said channel is between about two millimeters and about four millimeters in maximum depth, between about five centimeters and about seven centimeters in length and between about two centimeters and about three centimeters in maximum width.
 5. In a golf club head having a ball-impact face, a sole having a convex surface, a top, a back, a heel, a toe, and a hozzle, the improvement wherein an elongated concave depression is defined in said convex surface of said sole and said concave depression is aligned to extend from a location at said heel and proximate said ball-impact face away from said heel and at an acute angle of between about thirty degrees and about sixty degrees relative to said ball-impact face and said concave depression terminates inboard from said toe.
 6. A golf club head according to claim 5 wherein said depression is between about two millimeters and about four millimeters in maximum depth, between about five centimeters and about seven centimeters in length and between about two centimeters and about three centimeters in maximum width.
 7. A golf club head according to claim 6 wherein said depression is aligned at an angle of between about forty-five degrees and about fifty-five degrees relative to said ball-impact face.
 8. A golf club head according to claim 6 wherein said depression is aligned at an angle of about fifty degrees relative to set ball-impact face.
 9. A golf club head according to claim 8 wherein said ball-impact face has an arithmetic mean of profile roughness of between about 0.67 microns and about 0.81 microns, said sole has an arithmetic mean of profile hardness of between about 0.82 microns and about 1.1 microns, and said top has an arithmetic mean of profile roughness at least about three times as great as that of said ball-impact face and at least about three times as great as that of said sole.
 10. A golf club head according to claim 9 wherein said top has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns.
 11. A golf club head according to claim 10 wherein said back also has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns.
 12. In a golf club head having a ball-impact face, a sole, a top, a back, a heel, a toe, and a hozzle, the improvement wherein said ball-impact face has an arithmetic mean of profile roughness of between about 0.67 microns and about 0.81 microns, said sole has an arithmetic mean of profile roughness of between about 0.82 microns and about 1.1 microns, and said top has an arithmetic mean of profile roughness at least about three times as great as that of said ball-impact face and it least about three times as great as that of said sole.
 13. A golf club head according to claim 12 wherein said top has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns.
 14. A golf club head according to claim 13 wherein said back also has an arithmetic mean of profile roughness of between about 3.3 microns and about 3.9 microns.
 15. A golf club head according to claim 12 wherein said sole is formed with a convex surface that extends to said heel, said toe, said back, and said ball-impact face, and an elongated, concave depression is defined in said convex surface of said sole and said concave depression is aligned to extend from a location at said heel and proximate said ball-impact face away from said heel and at an acute angle of between about thirty-five degrees and about sixty-five degrees relative to said ball-impact face.
 16. A golf club head according to claim 15 wherein said depression is between about two millimeters and about four millimeters in maximum depth, between about five centimeters and about seven centimeters in length, and between about two centimeters and about three centimeters in maximum width.
 17. A golf club head according to claim to 16 wherein said depression is aligned at an angle of about forty-five degrees relative to said ball-impact face. 